Java 9 中 Optional.ifPresentOrElse() 和 Optional.or() 方法之间的区别?
javaobject oriented programmingprogramming更新于 2024/5/6 14:26:00
Java 9 版本引入了 Optional.ifPresentOrElse() 和 Optional.or() 方法以改进其功能。Optional.ifPresentOrElse() 方法检查值是否存在，应用具有值的操作，否则返回空操作，而 Optional.or() 方法检查值是否存在，返回包含值的选项，否则返回 Optional 应用于供应商功能。 Optional.ifPresentOrElse() 方法包含两个参数，Consumer 和 Runnable ，而 Optional.or() 方法仅包含一个参数，Supplier。
Optional.ifPresentOrElse() 的语法:
public void ifPresentOrElse(Consumer<? super T> action, Runnable emptyAction)
示例
import java.util.Optional;
import java.util.concurrent.atomic.AtomicInteger;
public class IfPresentOrElseMethodTest {
public static void main(String args[]) {
optionalIsPresent();
optionalIsEmpty();
}
private static void optionalIsPresent() {
Optional<String> optional = Optional.of("Test");
AtomicInteger successCounter = new AtomicInteger();
AtomicInteger emptyOptionalsCounter = new AtomicInteger();
optional.ifPresentOrElse(x -> successCounter.incrementAndGet(), () -> emptyOptionalsCounter.incrementAndGet());
System.out.println(successCounter.get());
System.out.println(emptyOptionalsCounter.get());
}
private static void optionalIsEmpty() {
Optional optional = Optional.empty();
AtomicInteger successCounter = new AtomicInteger();
AtomicInteger emptyOptionalsCounter = new AtomicInteger();
optional.ifPresentOrElse(x -> successCounter.incrementAndGet(), () -> emptyOptionalsCounter.incrementAndGet());
System.out.println(successCounter.get());
System.out.println(emptyOptionalsCounter.get())
}
}
输出
1 0 0 1
Optional.or() 的语法:
public Optional<T> or(Supplier<? extends Optional<? extends T>> supplier)
示例
import java.util.Optional;
public class OptionalOrMethodTest {
public static void main(String args[]) {
optionalIsPresent();
optionalIsEmpty();
}
private static void optionalIsPresent() {
Optional<String> optional1 = Optional.of("Test1");
Optional<String> optional2 = Optional.of("Test2");
Optional<String> optional3 = optional1.or(() -> optional2);
System.out.println(optional3.get());
}
private static void optionalIsEmpty() {
Optional<String> optional1 = Optional.empty();
Optional<String> optional2 = Optional.of("Test2");
Optional<String> optional3 = optional1.or(() -> optional2);
System.out.println(optional3.get());
}
}
输出
Test1 Test2
